Thermally responsive electrical device



Patented Sept. 12, 1950 UNITED STATES PATENT OFFICE Kirk A. Oplinger, Verona, and Stephen Sentipal,

East McKcesport, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application February 24, 1947, Serial No. 730,430

8 Claims. (Cl. 297-12) This invention relates to a thermally-responsive device and it has particular relation to thermal devices which are directionally responsive to the product of two variable quantities, such as the voltage and current of an electrical circuit.

Thermally-responsive devices are employed in the prior art for various purposes, such as for relaying and measuring. As shown in the Johnson Patent No. 2,323,776, thermally-responsive devices may be employed as directional relays. Depending upon the connection employed, the thermally-responsive relays may be designed to respond to the direction of flow 01 either real or reactive power. In addition, thermally-responsive devices are often employed for measuring the power or power demand of an electrical circuit. A device suitable for such measurements is disclosed in the Vassar Patent No. 2,323,788. Such an instrument may measure real or reactive power.

Ln accordance with the invention, a, thermallyresponsive device is provided which is of sturdy construction and which is substantially free of friction. The invention contemplates the utilization of a plurality of thermomotive elements which preferably are of the multi-metallic type. A thermomotive element may be defined as an element which, in response to a change of the temperature thereof, has one part which deflects or moves with respect to another part thereof. Multi-metallic elements are constructed of two or more layers of material which have different temperature coemcients of expansion. The most common form of a multi-metallic element consists of two layers and is known as a bimetallic element. However, three or more layers may be employed, depending upon the characteristics desired.

In a preferred embodiment of the invention, four multi-metallic elements are disposed substantially in a common plane and in side-by-slde relationship. Adjacent ends of the elements are electrically connected to provide two pairs of series-connected elements. The free ends of the elements are mechanically secured to each other and to a suitable support. By suitably energizing the elements from a source of electrical energy, the elements are subjected to stresses which tend to move the series-connected ends in opposite directions. The elements are preferably symmetrically arranged with reference to an axis which passes through suitable translating means and may be designed to produce a resultant force passing through the axis. Under such conditions, the resultant force does not produce a couple about the axis and no twisting of the elements about the axis results.

The translating means may comprise a pointer and scale which are designed to measure the deflections of the thermomotive elements for the purpose oiindicating the magnitude of the energization of the elements. Alternatively, the means may include electrical contacts which are actuated in response to variations in the energization of the thermomotive elements for the purpose of operating suitable electrical apparatus.

Itv is, therefore, an object of the invention to provide an improved thermally-responsive device capable of developing a resultant -force which does not exert a couple about a predetermined axis.

It is a further object of the invention to provide a thermally-responsive device wherein four thermomotive elements are disposed in a common plane substantiallyin side-by-side relationship and having adjacent ends electrically con- Y nected to'provide elements.

Other objects of the invention will be apparent from the description taken in conjunction with the drawing, in which:

Figure 1 is a top plan view of a thermallyresponsi're device embodying the invention with certain electrical connections schematically shown.

Fig. 2 is a view in end elevation of the thertwo series-connected pairs or many-responsive device shown in Fig. 1.

Fig. 3 is a view in top plan of a thermallyresponsive device, representing a modified embodiment of the invention and having electrical connections schematically shown, and

Fig. 4 is a view in and elevation of the thermally-responsive device shown in Fig. 3.

Referring to the drawing, Figure 1 shows a thermally-responsive device having a base i constructed of a suitable insulating material. The base I has a pedestal 3 mounted thereon and constructed of an insulating material. The base and pedestal may be molded from a phenolic resin. Three parallel electroconductive machine screws 5, I and 9 pass through the base and pedestal for the purpose of securing to the pedestal 3 electroconductive plates ll, l3 and I5. Nuts I! may be employed in association with the screws for securing'the plates to the pedestal and base. Thumb nuts ID are also provided for the machine screws to permit utilization of the machine screws as terminals or binding posts.

The plates H, il and II have secured thereto, by welding or otherwise, four thermomotive elements 2i, 23, 25 and 27. As shown in Figure 1. plate It projects beyond the pedestal 3 for the purpose of providing an overhanging lip ii to manner, the elements 23 and 23 are connected together by a bridge 2|. The bridges may be constructed of steel which is welded or otherwise suitably secured to the associated elements.

The elements 2|, 23, 23 and 21 preferably are multl-metallic elements. As shown more clearly in Fig. 2, the elements are formed of two laminations or layers a and b which are secured to form a bimetallic element in a manner well known in the art. For the purpose oi illustration, it will be assumed that the lamination b has a larger temperature coefllcient of expansion than that of the lamination a. As noted in Fig. 2, the laminations b of the elements 2| and 21 are located below the laminations a. Consequently, as the elements are heated they tend to deflect the bridge 28 in an upward direction away from the base By inspection of Fig. 2, it will be observed that the elements 23 and 25 have their laminations at below their laminations b. Consequently, when these laminations are heated, they tend to deflect their associated bridge 3| toward the base i.

The two bridges 29 and 3| are mechanically connected to each other but are electrically insulated from each other. Two insulating washers 33 and 35 are disposed on opposite sides of the two bridges and screw 31 passes through the washers and between the bridges. The screw may be constructed of insulating material or it may pass through a tube (not shown) of insulating material. Nuts 39 and 43 may be associated with the screw for securing the washers 33 and 33 together with the bridges 23 and 3| therebetween.

Since the bridges 29 and 3| are mechanically connected to each other, it follows that they must deflect as a unit in response to a change in the energization of the thermomotive elements. It will be recalled that the stress developed by the thermomotive elements 2| and 21 opposes that developed by the elements 23 and 23. Since the elements are similar in construction and shape, it follows that variations in ambient temperature have substantially no effect on the thermallyresponsive device.

In order to explain briefly the procedure for energizing the thermomotive elements, it will be assumed that the thermally-responsive device is associated with a circuit comprising the conductors Li and L2 for the purpose of responding to the flow of power in the circuit. The plates H and I3 are connected respectively through conductors 43 and 45 to the terminals of the secondary winding 41 of a voltage transformer 33. The primary winding of the voltage transformer is connected across the conductors LI and L2. The device is also energized in accordance with current flowing through the conductor L2 by means of conductors and 33 which are connected respectively to a center tap on the secondary winding 31 and to the plate l3.

Although the circuit with which the device is associated may be any desired alternating-current circuit, it may be assumed for the purpose of discussion that it is a single-phase, alternating-current circuit operating at a frequency of 60 cycles per second. Let it be assumed that for normal conditions oi power flow, the voltage transformer 33 supplies to the device a current component t. Let it be assumed further that current flowing through the conductor L2 divides between the conductors 33 and 43 equally, to provide current components ii therein. The arrows represent instantaneous directions of current flow. By inspection of Figure 1, it will be observed that the thermomotive elements 2| and 21 are energized in accordance with the sum oi the components n+1], whereas the thermomotive'elements 23 and 23 are energized in accordance with the difl'erence between the current components u-i1. Since the resultant current flowing through the elements 2| and 21 islarger than the resultant current flowing through the elements 23 and 23, the resistance losses in the former are greater than those in the latter elements. Consequently, the temperatures or the elements 2| and 21 are higher than those oi elements 23 and 23 and the stresses applied by the elements 2| and 21 to the bridge 23 exceed those applied by the elements 23 and 23 to the bridge 3|. Consequently. in response to an increase in such energization, the bridges move away from the base until a position or equilibrium is reached.

Let it be assumed next that the directibn oi power flow in the circuit represented by the conductors LI and L2 reverses. This may be represented by assuming that the current components i1, shown in Figure 1. reverse in direction. Such a reversal produces an alternating-current flow through the elements 2| and. 21 which is equal to the diilference between the components io-ii, whereas the alternating flow through the elements 23 and 23 is equal to the sum or thecomponents is-i-ii. The stresses developed by the elements 23 and 23 consequently exceed those developed by the elements 2| and 21 and the bridges 23 and 3| are moved towards the base i until I. new position of equilibrium is reached.

It the movement of the bridges relative to the base is measured by suitable translating means, such as a scale and pointer, it will be round that the direction of movement of the bridges from the positions they occupy when the elements are unenergised is dependent upon the direction of power flow in the associated circuit. The extent of the movement is dependent on the magnitude of the aforesaid power flow. It the voltage applied to the primary winding of the transiormer 43 is in phase with that across the conductors Li and L2, the movement or the bridges is dependent on the real power flowing in the associated circuit. It the voltage applied to the primary winding of the transformer 33 is in quadrature with the voltage across the conductors LI and L2, the movement oi the bridges depends upon the flow of the reactive power in the associated circuit.

Movement of the screw 31 may be employed tor actuating translating means suitable for controlling any desired electrical apparatus. To this end, a movable contact 3| is secured through an electroconductive spring 33 to a terminal or binding post 33 which may be secured to the base A stationary contact" is secured to the base lbymeansotaterminalorbindingpost "and an electroconductive strip I I. The spring 33 biases the contact 3| away from the contact 31. By inspection 01' Fig. 2, it will be observed that when the screw 31 is deflected toward the base it engages the contact 3| and moves the contact 3| into engagement with the contact 31. Such movement closes a circuit connected to the binding posts .6! and 80. Consequently, the device 0! Figure 1 and Fig. 2 constitutes a directional relay which closes its contacts in response to a reversal oi power flow in the associated circuit.

The elements 23, and 25 preferably are spaced apart by a substantial distance in order to assure operation oi. all elements at the same temperature when they are energized only by the component ic- It will be noted that the elements are symmetrically disposed about an axis X-X which passes through the screw 31. (lousequently, the resultant stress of the element always passes through the axis Iii- X and no couple is developed about the axis. For this reason no undesirable angular movement of the elements about the axis X-X takes place.

In the embodiment shown in Figs. 3 and 4., a base la and a pedestal 3a are shown, which correspond to the base and pedestal shown in Fig. 1 and which may be similarly constructed. The screws, 1 and 8 are employed for attaching electroconductive plates Ila, 13a and 15a to the pedestal 3a and base la. ,These plates have welded or otherwise electrically secured thereto lour thermomotive elements Zia, 21a, Ila and a. The element 23a is secured to the plate lid. The elements Ila and 25a are connected to the plate ita. The element 21a is connected to the plate lid. The elements ila and 21a are electrically and mechanically connected in series by means 01' a bridge 29a, whereas the elements 230. and 250. are electrically and mechanically connected in series by a bridge 3la. The elements lid and 21a and the bridge 28a may be formed from a strip of bimetallic material by cutting a slot I2 in the strip. Similarly the elements 23a and 25a, together with thebridge ,3ia may be formed by cutting a slot 18 in a strip of bimetallic material.

As shown in Fig. 4, all elements have a. layer b located beneath the layer a. Consequently, in response to changes in ambient temperature, all of the elements deflect in the same direction relative to the base la, and the position of the bridge 28a relative to the bridge 3 la remains unchanged; However, if a temperature diilerence exists between the elements 23a and 25a on one hand and the elements Zia and 21a on the other hand,the bridges 28a and 3 in. are displaced relative to each other from the relative positions they occupy when the device is deenergized.

For energizing the elements, the secondary winding 41 of the transformer 48 has its terminals connected to the plates Ila and ila through conductors 48a and a which correspond respectively to the conductors I3 and 45 of Figure 1. The center tap of the secondary wind:-

ing 41 and the plate i3a are connected to conductors ila and 53a which correspond to the conductors 8i and 53 of Figure 1 and which are connected similarly to the associated electrical circuit.

With the connections, as shown in Fig. 3, the current components is and i1 may have instantaneous directions of flow similar to those depicted by arrows. With such energization, the elements 2 la and 21a are energized in accordance with the sum of the components ie+il, whereas the elements 23a and 25a are energized in accordance with the difference between the components iii-i1. Therefore, the temperature of the eleasaaecs I numerous modifications are possible.

ments 2 la and 21a is greater than that of the elements 23a and 25a and the bridge 28a is deflect- 6 ed away from the base i by a distance substan-- tially greater than that of the bridge tla.

I! thedirection or power in the associated electrical circuit reverses, theelements did and 25a are energized in accordance withthe sum of the components l+ii and the elements Ila and 210. are energized in accordance withfitheniiflerence between these components. In the last-mentioned case, the bridge Ola would be deflected away from the base la to an extent greater than thedeflection oi the bridge 29a from the base;

If translating means in the form oi. a pointer and scale were mounted respectively on the bridges Ila and No, the direction of deflection of the bridge liarelative to the bridge 3la would depend upon the direction of power flow in the associated circuit, .and the magnitude of the.

deflection would depend on the magnitude of the power flow.

The translating means associated with the bridges 28a and Sin may take the form 01' a double contact 15 which is secured to the bridge ila in any suitable manner for movement therewith. A conductor 11 may be electrically connected to the contact" through the plate i5a or otherwise An insulating fork 19 is secured to the bridge 29a in any suitable manner as by rivets (not shown). The fork 19 carries two contacts 8i and 83 positioned in the path of movement of the double contact 15. The contacts 8i and 83 are connected to flexible conductors 85 and 81. 11' the bridge 3ia deflects in an upward direction (as viewed in Fig. 4) relative to the bridge 28a, the contacts 8i and I5 engage to complete a circuit associated with the conductors I1 and 85. Such a circuit may be the tripping circuit of an associated circuit breaker which may be employed to control any desired electrical apparatus. Should the bridge 3ia move in a downward direction relative to the bridge 29a, the contacts 15 and 83 engage to complete a circuit associated with the conductors 11 and 81. Consequently, closure of the contacts I5 and 83 may be employed for any desired control operation. From this discussion it is apparent that the device shown in Figs. 3 and 4 is a directional relay which selectively closes either of two pairs of contacts in accordance with the direction or power in an associated electrical circuit. Since the bridges 28a and 3ia are not rigidly connected to each other, the stresses required for an operation may be substantially less than those developed in the thermomotive elements shown in Figure 1.

Although the invention has been described with reference to certain specific embodiments thereof,

All modiflcations falling within the spirit and scope of the invention are intended to be covered by the appended claims.

We claim as our invention:

1. In a thermally-responsive device, a first pair of thermomotive elements disposed in parallel, side-by-side relationship and electrically connected in series at adjacent ends thereof, a second pair of thermomotive elements disposed in parallel, side-by-side relationship and electrically connected in series at adjacent ends thereof, a support for the free ends of the thermomotive elements normally maintaining the elements in unstressed condition, whereby said pairs may be energized electrically through the free ends respectively in accordance with the sum and difterence of two variable quantities, and means diii'erentially responsive to the stresses developed 7 in said pairs of thermmnotive elements, said support comprising an electrical connection between one 01! the free ends oi each of the pairs.

2. In a thermally-responsive device, a first pair of thermomotive elements disposed in parallel, side-by-side relationship and electrically connected in series at adiacent ends thereof. a second pair or thermomotive elements disposed in parallel, side-by-side relationship and electrically connected in series at adiaunt ends thereof, a support for the free ends of the thermomotive elements normally maintaining the elements in unstressed condition, whereby said pairs may be energised electrically through the free ends respectively in accordance with the sum and diiierence of two variable quantities, and insulating means mechanically connecting the series-connected ends or the thermomotive elements for movement as a unit relative to the support, said support comprising an electrical connection between one of the tree ends each of the pairs.

3. In a thermally-responsive device, a first pair of thermomotive elements disposed in parallel, side-by-side relationship and electrically and mechanically connected in series at adjacent ends thereof, a second pair of thermomotive elements disposed in parallel, side-by-side relationship and electrically and mechanically connected in series at adjacent ends thereof, a support for the tree ends of the thermomotive elements, whereby said pairs may be energised electrically through the free ends respectively in accordance with the sum and diiierence oi two variable quantities, and means responsive to relative movement between the pairs of thermomotive elements at the series-connected ends thereof, said four elements being substantially in a common plane when deenergized.

4. In a thermally-responsive device, a support, iour thermomotive multi-metallic elements disposed in parallel, side-by-side relationship substantially in a common plane and having adjacent ends mechanically secured to the.support, first means electrically connecting the free ends of the inner multi-metallic elements, second means electrically connecting the free ends of the outer multi-metallic elements, and means diiierentially responsive to the forces tending to deflect the first and second means relative to the support.

5. In a thermally-responsive device,a support, tour thermomotive multi-metallic elements disposed in parallel, slde-by-side relationship substantially in a common plane and having adjacent ends mechanically secured to the support, first means electrically connecting the free ends oi the inner multi-metallic elements, second means electrically connecting the free ends oi the outer multi-metallic elements, said inner multimetallic elements and said outer multi-metallic elements tending to deflect in opposite directions out of said plane in response to an increase in temperature thereof, and insulating means securing the free ends of the multi-metallic elements for movement as a unit relative to said adjacent ends.

6. In a thermally-responsive device, a support, iour thermomotive multi-metallic elements disfiection occurring between said pairs of multi-' metallic elements.

7. In a thermally-responsive device, four parallel side-by-side electroresponsive thermomotive elements extending betweenr first and second,

' spaced stations substantially in a,,common plane,

a connection at the first station for connecting a first pair of the elements electrically in series, a connection at the first station for connecting a second pair of the elements electrically in series, said pairs being electrically and mechanically spaced from each other, a connection at the second station for electrically connecting one element in each or said pairs to each other, a mechanical support at the second station for the four elements, and a translating device diflerentially responsive to the outputs of the pairs of thermomotive elements.

8. In a thermally-responsive device, four parallel side-by-side electroresponsive thermomotive elements extending between first and second spaced stations substantially in a common plane,

a connection at the first station for connecting a first pair oi the elements electrically in series, a connection at the first station for connecting a second pair of the elements electrically in series, a mechanical support at the second station for the four elements, circuit connections connected to the pairs at the second station for directing a first current component in series through the pairs of elements, said circuit connections being effective for directing a second current compo-' nent in parallel through the pairs of elements, whereby the pairs are energized in operation in accordance respectivelywith the sum and difierence of the current components, and a translating device diiierentially responsive to the outputs of the pairs of elements.

KIRK A. OPIJNGER. STEPHEN SENTIPAL.

REFERENCES CITED The iollowing references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,831,558 Hall l Nov. 10, 1031 2,055,705 Prinz Sept. 20, 1936 2,112,047 Rick Mar. 22, 1938 2,225,975 Bruce Dec. 24, 1940 2,284,383 Elmer May 26, 1042 2,300,810 Jones Dec. 29, 1042 FOREIGN PATENTS Number Country Date 594,744 Germany Mar. 21, 1034 

